How the ring size calculator works
You can estimate ring size from finger circumference or from the inside diameter of a ring that already fits. The calculator converts your measurement to millimeters and compares it with common US ring size relationships.
Ring size measurement
diameter = circumference ÷ π
The calculator then estimates the closest US ring size from the inside diameter.
Example
A finger circumference of 54.5 mm corresponds to an inside diameter of about 17.35 mm, which is close to US ring size 7.
Use this tool when you want to calculate ring size from a finger measurement or when you are trying to find my ring size before ordering. It gives an estimated US size that should be checked against the seller or jeweler sizing chart.
Frequently asked questions
Which measurement is better?
A correctly measured finger circumference is useful, while measuring the inside diameter of a ring that already fits can also work well. Use a jeweler's chart for the final purchase.
Why can ring size vary by brand?
Manufacturing tolerances, ring width, shape, and sizing standards can affect fit. The calculator is an estimate rather than a replacement for the seller's sizing chart.
Should I measure when my fingers are cold?
Cold temperatures can temporarily change finger size. A comfortable room temperature is usually a better time to measure.